Heat exchanger



ep 1952 J. BLIZARD 2,609,797

HEAT EXCHANGER Filed June 9. 1948 2 SHEETS-SHEET 2 INVENTOR Jay/v 52/2/09? Patented Sept. 9, 1952 HEAT EXCHAN GER John Blizard, Garden City, N. Y., assignor to Foster Wheeler Corporation, New York, N. Y., a corporation of New ,York

Application June 9, 1948, Serial No. 31,855

. 1 This invention relates to ratus and more particularly to apparatus for heating air.

The present invention provides apparatus whereby air to support combustion in a furnace 7 Claims. 01. 122-1) heat exchange appar 1 i heated by flowing in indirect; heat exchange 1 relationship with liquid, which liquid has been heated by passing in indirect heat exchange relationship with gases of combustion from the furnace.

This invention further provides heat exchange apparatus in which heated circulating liquid is used to heat air and wherein the volume of circulating liquid is varied in accordance with the temperature of the liquid.

The present invention also provides an air exchange relationship with gases of combustioni from the furnace and wherein the rate of flow of liquid passingin indirect heat exchange relationship with the gases of combustion and with the air corresponds to the flow of vapor from the vapor generator.

. The invention will be understood from the following description.when iconsidered in connection with the accompanyingdrawings forming a part thereof, andin which: Fig. l is a transverse vertical sectional view taken on the line l-I of Fig. 2;

a Fig. 2 is a plan view partly in elevation and partly in section taken on the line 2-2 of Fig. 1; Fig. 3 is a flow diagram of the apparatus of the present invention, and Fig. 4 is a partial transverse vertical sectional Y view of another embodiment of the invention.

Like characters of references refer to like parts throughout the several views.

Referring to the drawings, the apparatus of the present invention is disclosed as embodied in a vapor generator comprising a setting II) with an upper steam and water drum I I associated therewith. The setting II] has a combustion chamber Ill therein, which, chamber is fired by a plurality of burners I 2. A vertically inclined bank of vapor generator tubes I3 is disposed at one side of chamber I B, the tubes of which bank are in communication' at the top thereof with the liquid space of drum I I and at'the bottom with a liquid drum I4 which is ofiset to saidflone side of drum I I. bank of tubes [3 which superheater has an inlet I6 (Fig. 2);incommu'nication with a vapor out- A superheater I5 is positioned within the let conduit ll connected to the vapor space of steam and water drum II. Superheater' I5 has an outlet I5 (Fig. 2) in communication with superheated steam outlet conduit IB (Fig. 1). The roof I9 of setting It and the side wall 20 of said setting are lined by water wall tubes 2|, which tubes are in communication at the upper end thereof with the liquid space of drum I I and at the bottom with a header 22.

An outlet flue 22 providing a combustion'gas outlet passage 23 is positioned at the side of the bank of tubes I3 opposite to the side of said bank adjacent combustion chamber Ill. Passage 23 of flue 22 is in communication with the setting at the top thereof so that gases of combustion from chamberI I after flowing in heat exchange relationship with the bank of tubes I3 pass from the setting in passage 23 of flue 22. v

As shown, an economizersection 24 is positiorred in passage 23 of ,fiuefl 22' in the lower part of said flue, while a heat exchanger 25 comprising a pluralityof: superimposed spaced rows of spaced tubes. 26 is disposed in passage 23. above economizer 24.. The tubes 28. extend transversely of passage 23 so that gases of combustion flowing through the passage flow over said tubes. The tubes of each row 26 "are serially connected as are the adjacentrows of .thesuperimposed rows of tubes. The heat exchanger 25 has a fluid inlet 2'! in communicationwith the uppermost row of tubes and a liquid outlet. 28 in communication with the lowermost row of tubes. Liquid inlet 21 is in communication with the bottom of reservoir tank 29 through conduit 21. As shown, the tubes of economizer 24 and the tubes of heat exchanger 25 have extended surface members thereon. 1

Tank 01' reservoir 29, which is pressure-tight, is mounted above drum I i on supporting girders 30. As shown, the tank 29 hasa safety valve 3! and a vent 32 at the top thereof and also has a liquid gage 33 at one side of the tank. In order that the liquid flowing through heat exchanger 25 will not be vaporized in said heat exchanger, it is necessary toprovide means for maintaining the liquid under such pressure. that it will not boil while it is being circulated from thereservoir 29 through the heat exchanger 25. and into the tubes 46 of air heating heat exchanger .45, As shown in Fig.- 1, this is accomplished by providing a heating coil. disposed .slightly below the normal water level WL and above a baffle 29 having anopening I0 therein. The relatively small quantity of liquid between WL and baiiie 29' is thereby heated. -Coil 34 has a steam inlet ing to the pressure required on the liquid passingthrough exchanger 25 to avoid boiling, The bafile 29 prevents a substantial mixing of the relatively small quantity of liquid above the; baffle with the larger quantity of circulating liq- 7 uid below said baflle.

the flow of steam through inlet 35 into coil As shown, a valve H, which may be manually or automatically controlled is positioned in inlet and sufficient steam is permitted to flow through" coil 35 to heat the liquid above baffie 25' to a degree' substantialIy equal to the temperature of the liquid leaving heat exchanger 25 through 011+- let 2S. 7

"An air conduit comprising a top wall 31, an end wall 38, a bottom wall 59,-a forward wall :15, and"a rear wall-4| is disposed along the front wall 52 'of setting It) in which front wall of the setting the burners 12 are disposed. Each of the burners l2 have air inlet ports '43 through which The temperature of -the liquid above bafiie 29 is controlled by controlling heater l5 through superheate'r inlet 15. Passage of gases of combustion in heat exchange relationship with the superheater 15, as the gases ilow to flue 22', superheats the steam passing through said superheater. The superheated steam flows outwardlyof the superheater through superheated-steam outlet l5 and outlet conduit l8. 1

Liquid, for example, water, or a' high boiling point liquid such as diphenyl, diphenyl oxide or other desirable liquid in reservoir '25 above ba'fiie 29' is heated to the desired temperature, that is, to a temperature above that of the liquid I flowing throughsoutlet 28 of heat exchanger 25,

air to support combustion enters chamber it. 7

The air conduit has an inlet passage #34 through which air enters said passage. An air heating heat exchanger 55 comprising a plurality of apart is disposed in the air conduit in the path or flow of air frominlet passage 44 to ports 55 or burners i2. As shown, tubes 45 are vertically extending and arranged in a plurality of closely adjacent rows, the tubes ineach row being spaced from one another and the tubes of each row being spaced 'fromthe tubesof adjacent rows. Tubes 46 are connected atthe top thereof teen inlet header and at the bottom to an outlet header '48. Inlet header 4-1 is in communication with outlet 28 of heat exchanger 25 through a heated fluid conduit 49. Outlet header is of air heating heat exchanger #5 communi- .cates with the suction of a pump 55 through outlet conduit 5I. Thedischargeoof pump 50 communicates with the liquid space of tank 2?: through liquid conduit 52. As shown, the pump 50 is actuated by an electric motor 53.

ihe flow of liquid from the tank or reservoir 25 through heat exchangers 25 and E5 is controlled in response to the now of vapor fromthe vapor generator through superheated steam outlet conduit 18. As shown, this control comprises a pressure responsive device 55 in communication with conduit 18 at one side of an orifice 55 through pipe 51 and at the other side of said outlet through pipe 58. The pressure diiferential at opposite sides of the orifice 55 which is transmitted to opposite sides of a diaphragm as in device 55 actuates the diaphragm which in turn moves a contact arm 55 of a rheostat 5%. The rheostat is in communicationwith one pole of an electrical source through line 52 and with a connection of motor 53 through line 53 which line is connected toarm 60. The other connection of motor 53 communicates with opposite ole of said electrical source through line t l; r

In operation, vapor, is generated in the vapor generator by the flow of combustion gases from chamber I5 over bank of tubes it into passage by-rlowing steam through coil 34. This create sufficient pressure on the liquid in tank or reservoir 29 to prevent boiling of the liquid in heat exchanger 25. From tank 29, liquid under pressure flows downwardly through inlet conduit 21' into heat exchanger 25. ,The liquid thereafter flows through the heat' exchanger 25 .to liquid outlet 23 and is heated in the heat exchanger by passage in indirect heat exchange relationship with gases of combustion flowing through passage 23 of iiue 22'. The heated liquid passes from outlet 2-3 into heated fluid conduit 49 whence it fiows into inlet lieaderffll of the air heating heat exchanger '55. From the inlet header ll, the heated liquid passes through'tubes 55 of heat exchanger 45 into outlet header 43 anclis-withdrav/n from said header by pump 55 which withdraws the liquid from the heater through outlet conduit 5| 'thereafter'to discharge the liquid through liquid conduit '52 into reservoir 25. q

Air to be heated .ispa'ssedinto theair conduit through inlet passage 44 and flows in indirect heat exchange relationship with tubes 46 of air heating heat exchanger 45 and is thereby heated. After heating, 'th'e'air flows through ports lt of burners [2 into thecombustion chamber l0. The flow of liquid from the reservoir 29 through 'heat'excha'ngers 25 and '45 and thence back to the reservoir is controlled in response to conduit l8. For example, upon'an increase in thefiow of steam through outlet conduit l8,-there is an increase of pressure across theorifice 55 which increased pressure influences pressure responsive device 55 through pipe 51 to cause rheostat arm 65 to move 'in a clockwise direction thereby permitting -a greater flow of current through line 62 .torheostat 6|, arm 50, and'line st-toelectricrnotor 53. Increased flow of current to motor-53 increases the speed of the-motor and the pump 50 thereby increasing the rate of circulation of the liquid from the tank 29 through heatexchangers25 and 45 and through the line 52 to tank 29. Upon a decrease in the flow of steam through outlet conduit 18, the pressure responsive device 55 wouldcause the arnr'iifi of rheostat 6| to move-in a counterclockwise direction causing the resistance of rheostat tii'to be increasedanda lesser amount of current, to pass to"'niotor 5'3 therebydecreasing the s'peed'of pump '50 'and'the rate of circulation of liquid th'rough'heat exchangers 25 and 45. It will be understood that other flow controlling deviceswhich'confirolthe rate'of flow of fluid from reservoir '29 "through heat exchangers 25 and 45in response to "the now of steam through steam outlet {8 .may' be used.

In the-form of the invention shown in Fig. '4,

I the tank 29 is'lbf"cylindrical"shape and'does not require aba'ffie29"as'"shown in Fig. 1. Liquid from the lower portion of the tank passe into an outlet conduit 12 which outlet conduit is in communication at one end thereof with the lower portion of the tank and at the other end withconduitfl, Intermediate theopposite ends thereoflthe outlet conduit 12 is in communication with liquid conduit 52.

In operation, liquid from tank 29 passes therefrom through conduit 12 in which conduit it mixes ,with fluid lfrom air heat exchanger passed to conduit 12 through liquid conduit 52. The mixture ofliquid then flows from outlet conduit 12 into inlet conduit 27? thence into the inlet 21 of heat exchanger 25. Substantial mixing of the liquid adjacent the normal Water level WL in the upper part of tank 29, which liquid is heated by coil 34, with the liquid circulating through conduits 52, I2 and 2'! is prevented.

Inasmuch as changes may be made in the form, location, and relative arrangement of the several parts ofthe apparatus disclosed Without departing from the essentialcharacteristics of the invention, it will be understood that the in vention is not to be limited excepting by the scope of the appended. claims.

What is claimed is:

1. Heat exchange apparatus for heating a fluid by flowing said fluid anda liquid in indirect heat exchangeirelationship with one another, said apparatus comprising means forming a flow path for heated .gases,,a heat exchanger providing a liquid path of flow and positioned in indirect heat exchange, relationship with heated gases passing through said gas flow path, a pressuretight liquid reservoir so constructed and arranged that liquid therein is normally maintained under pressure, a heating coil within said reservoir below the normalliquid level therein adapted to vaporize liquid in indirect heat exchange relationship with said coil and thereby create pressure in the reservoir, means through which liquid is conducted from the reservoir into said liquid path of flow of theheat exchanger, a fluid conduit for conducting fluid to be heated, another heat exchanger providing a liquid path of flow with a liquid inlet and a liquid outlet, the other heat exchanger being positioned in indirect heat exchange relationship with fluid flowing in the fluid conduit for conducting fluid to be heated,

means for conducting heated liquid from the first-mentioned heat exchanger to the inlet of the liquid path of flow of the other heat exchanger, conduit means in communication with the outlet of said other heat exchanger and with the liquid path of flow of the first-mentioned heat exchanger, circulating means associated with said last-mentioned conduit means for circulating liquid therethrough and control means associated with the heating coil and adapted to control the generation of vapor and pressure within the reservoir to maintain the liquid therein below its boiling point.

' 2; Heat exchange apparatus for heating a fluid byflowing said fluid and a liquid in indirect heat exchange relationship withone another, said apparatus comprising means forming a flow path for-heatedgases, a heat-exchanger providing a liquid path of flow and-positioned in indirect heat exchange relationship with heated gases passing through said gas flow path, a pressuretight liquid reservoir having a top and bottom and a normal liquidlevel intermediate said top and bottom, saidreservoir being so constructed and arranged that liquid therein is normally maintained under pressure, a heating coil within said reservoir below the normalliquid level and above said bottomtoffthe reservoir, a baffle dis- Iposed 'aboveltheibotto'm of the reservoir and below'the said heating coil, the baflle dividing the reservoir into upperand lower compartments and having a liquid opening therein through which said compartments communicate with one another, said cell being adapted to vaporize the liquid in the upper compartment and thereby create pressure in"the reservoir, means through which liquid isconducted from the lower part of thereservoir into said liquid path of flow of the heat exchanger, a fluid conduit for conducting fluid to be heated, said fluid conducting means having a fluid inlet and a fluid outlet, an-

other heat exchanger providing a liquid path of flow with a liquidinlet and a liquid outlet,

the other heat exchanger being positioned in ated with the heating coil and adapted to control the generation of vapor and pressure within the reservoir to maintain the liquid therein below its boiling point! 3. Heat exchange apparatus for heating a fluid by flowin said fluid and a liquid in indirect heat exchange relationship with one another, said apparatus comprising means forming a flow path forfheated gases, a heat exchanger providing a liquid path of v flow and positioned in indirect heat exchange relationship with heated gases passing through said gas flow path, a pressuretight liquid reservoir having a top and bottom j and a normal liquid level intermediate said top and bottom, said reservoir being so constructed and arranged that liquid therein is normally maintained under pressure, a steam heating coil within said reservoir below the normal liquid level and above said bottom of the reservoir, said coil having a steam inlet and a steam outlet, means for controlling the flow of steam through said coilto control the generation of vapor and pressure Within the reservoir to maintain the liquid'therein below its boiling point, a baflie disposed above the bottom of the reservoir and below the said heating coil, the baffle dividing the reservoir into upper and lower compartments and havin a'liquid opening therein through which said compartments communicate with one another, said coil being adapted to vaporize the which liquid is conducted from the lower part means havinga fluid inlet and a fluid outlet,

another heat exchanger providing a liquid path of flow with a liquid inlet and a liquid outlet, the

other heat exchanger being positioned in indirect heat exchange relationship with fluid flowing in the fluid conduit for conducting fluid to be heated-means for conducting heated liquid from the first-mentioned heat exchanger to the inlet of the liquid path of 'flow'of the other heat exchanger, conduit means in communication with the outlet of said other heat'exchanger and with the liquid pathjof flow of the first-mentioned heat exchanger, andcir'cula'tin'g means associated with said last-mentioned conduit means for circulating liquid therethrough. v

4. Heat exchange apparatus for heating a fluid by flowing said'fluid'and a liquid in indirect heat exchange relationshipwith one another, said apparatus comprising means forming a flow path for heated gases, aheat exchanger providing a liquid. path of flow and positioned in indirect heat exchange relationship with heated gases passing through said gas flow path, a pressure tight liquid reservoir so constructed and arranged that liquid therein is normally maintained under pressure, a heating coil within said reservoir below the normal liquid level therein adapted to vaporize liquid in indirect heat ex change relationship with said coil and thereby create pressure in the "reservoir, a liquid outlet conduit in communication .at one end thereof with said reservoir substantially belowsaid'heating coil and at the opposite end with said liquid path of flow of the heat exchanger, a fluid conduit for conducting fluid to be heated, said fluid conductingm'eans having a fluid inlet and a fluid outlet, another heat exchanger providing a liquid path of flow with a liquid inlet and aliquid outlet,"the other heat exchanger being positioned in indirect heat exchange relationship with fluid flowing in the fluid conduit for conducting fluid to be heatedmeansior conducting heated liquid from the first-mentioned heat exchanger to the inlet of the liquid path of flow of the 'otherheat exchanger, conduit means for conducting liquid from the 'c'utl'etof said other heat exchanger, saidlast-me'ntioned conduit means being incommunication at one end thereof with the outlet of'the other heat exchanger and at the opposite end thereof with'the liquid outlet conduit intermediate the'opposite ends of said liquid outlet conduit, circulating means associated with said last-mentioned conduit means for circulating liquid therethrough, and control means associated with the heating coil and adapted 'tocontrol thegeneration of'vapor andpressure within the'reservoir to maintain theliquid therein below its b'oilingp'oint.

7 '5. Heat exchange apparatus for heating air to support combustion in a vapor generator having a combustion chamber by flowing said air and a liquid in indirect heat exchange relationship with one another, means for firing said chamber, a combustion gas'outlet, and vapor generating means in heat exchange relationship with gases of combustion, the vapor generator having a vapor outletsaidheat exchange apparatus comprising a heat exchangerproviding a liquid flow path and positioned in heat exchange relationship with gases of combustion passing 'from the combustion chamber to said gas outlet, aliquid reservoir disposed at a higher elevation than said 7 heat exchanger, said reservoir being so .con-

path of the heat exchanger, air conducting means for conducting air .to the combustion "chamber, said air conducting means having an 7 air inlet adapted to receive air to be heated and air outlet in communication with thecombustion chamber, another heat exchanger providing another liquid flow path, said other liquid flow path having a liquid inlet "and a liquid outlet, the other heat exchanger being positioned in heat exchange relationship with air passing 'irom the air conducting means inlet to the air conducting means 'outlet,'means for conducting heated liquid from the first-mentioned heat exchanger to the inlet of said other heat exchanger, a pump having' its suction in communication with the outlet of said other heat exchanger and its discharge in communication with the reservoir, control means associated with the heating coiland adapted to control the generation of vapor and pressure within the reservoir to maintain the liquid therein below its boiling point, a motor for actuatin said pump, and other control means associated with the motor and with said vapor outlet and adapted to control the motor and thereby control the speed of the pump in response to the flow of vapor through the vapor outlet.-

6. Heat exchange apparatus for heating air to support combustion in a vapor genera-tor having a combustion chamber-by flowing said air and a liquid in indirect heat exchange relationship with one another, means for firing said chamber, a combustion gas outlet, and vapor generating means in heat exchange relationship with gases of combustion, the vapor generator having a ivap or outlet, said heat exchange rapparatus comprising a heat exchanger providing a liquid flow path and positioned inhe'at exchange relationship with gases of combustion passing from the combustion chamber .to said gas outlet, a liquid reservoir having a top and bottom and a normal liquid level intermediate said top and bottom, said reservoir being so constructed and arranged that liquid therein is normally maintained under pressure, a heating ,coil within said reservoir below the normal liquid level and above said bottom .of the reservoir, a bafiledisposed above the bottomlof the reservoir and elow the saidheating coil,:the bailie dividing the reservoir into upper and lower compartments and having a liquid opening therein through which said compartmentscommunicate Withone another, said coil being adapted to vaporize the liquid in the upper compartment and thereby create pressure in the reservoir, means through which liquid is "conducted from the lower part of the reservoir into said flow path of the :heat exchanger, 'air'conducting means for conducting air to the combustion chamber, said air .con-

ducting means having an air inlet adapted to receive air to 'berheated and air outlet incommunication with the combustion chamber, another heat exchanger providing another liquid flow path, said other liquid flow-path having a liquid inlet and a liquid outlet, the other heat exchanger being positionedyin-heat exchangerelationship with air passingfromthe air conducting means inlet to the air conducting means outlet, means for conducting heated liquid 'from the first-mentioned -heat exchanger to the inlet of associated with the heating coil andadapted to control the generation of vapor and pressure within the reservoir to maintain the liquid therein 'below its boiling point,-a motor for actuating said pump, and other control means associated with the motor and with said vapor outlet and adapted to control the motor and thereby control the speed of the pump in response to the flow of vapor through the vapor outlet.

7. Heat exchange apparatus for heating air to support combustion in a vapor generator having a combustion chamber by flowing said air and a liquid in indirect heat exchange relationship with one another, means for firing said chamber, a combustion gas outlet, and vapor generating means in heat exchange relationship with gases of combustion, the vapor generator having a vapor outlet, said heat exchange apparatus comprising a heat exchanger providing a liquid flow path and positioned in heat exchange relationship with gases of combustion passing from the combustion chamber to said gas outlet, a liquid reservoir so constructed and arranged that liquid therein is normally maintained under pressure, a heating coil below the normal liquid level in said reservoir and adapted to generate vapor by heating the liquid and thereby create pressure in the reservoir, a liquid outlet conduit in communication at one end thereof with said reservoir substantially below said heating coil and at the opposite end with said liquid path of flow of the heat exchanger, air conducting means for conducting air to the combustion chamber, said air conducting means having an air inlet adapted to receive air to be heated and air outlet in communication with the combustion chamber, another heat exchanger providin another liquid flow path, said other liquid flow path having a liquid inlet and a liquid outlet, the other heat exchanger being positioned in heat exchange relationship with alr passing from the air conducting means inlet tothe air conducting means outlet, means for conducting heated liquid from the first-mentioned heat exchanger to the inlet of said heat exchanger, a pump having its suction in communication with the outlet of said other heat exchanger and its discharge in communication with the liquid outlet conduit intermediate the opposite ends of said liquid outlet conduit, control means associated withthe heating coil and adapted to control the generation of vapor and pressure Within the reservoir to maintain the liquid therein below its boiling point, a motor for actuating said pump, and other control means associated with the motor and with said vapor outlet and adapted to control the motor and thereby control the speed of the pump in response to the flow of vapor through the vapor outlet.

JOHN BLIZARD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PAENTS Number Name Date 1,064,037 Whitney June 10, 1913 1,235,928 Sargent et al Aug. 7, 1917 1,681,926 Bell Aug. 28, 1928 1,708,303 Downs Apr. 9, 1929 1,833,130 Roe Nov. 24, 1931 1,927,215 Peebles Sept. 19, 1933 1,975,519 Rudorfi Oct. 2, 1934 2,072,166 Goodman Mar. 2, 1937 2, 15,548 Artsay Apr. 26, 1938 2,335,655 Dickey Nov. 30, 1943 FOREIGN PATENTS Number Country Date 299,436 Great Britain Oct. 26, 1928 

